The interaction between biotin and avidin or streptavidin is considered to be practically irreversible. Biotin has a affinity constant, or KD, for avidin of about 10−15 M. While the interaction provides an excellent means for capturing biotin-containing entities, releasing those entities once captured requires very harsh conditions, such as a strong acid, detergent, and/or high temperature. Such conditions include, for example, boiling in high salt; formamide and EDTA heated to 94° C.; 6 M guanidine, pH 1.5; and heating to at least 65° C. in the presence of salt, SDS, and EDTA. Such conditions are generally not suitable for purification of proteins or viable cells or viruses.